1. Field of the Invention
The invention generally relates to a method and apparatus for supporting and transferring substrates during photomask fabrication.
2. Background of the Related Art
Semiconductor device geometries have dramatically decreased in size since such devices were first introduced several decades ago. Since then, integrated circuits have generally followed the two year/half-size rule (often called Moore""s Law), which states that the number of devices on a chip doubles every two years. Today""s fabrication plants are routinely producing devices having 0.35 xcexcm and even 0.18 xcexcm feature sizes, and tomorrow""s plants soon will be producing devices having even smaller geometries.
As the fringes of sub-micron technology are pressed, the increasing circuit densities have placed additional demands on processes used to fabricate semi-conductor devices. For example, as circuit densities increase, the widths of vias, contacts and other features, as well as the dielectric materials between them, decrease to sub-micron dimensions, whereas the thickness of the dielectric layers remains substantially constant, with the result that the aspect ratios for the features, i.e., their height divided by width, increases. Reliable formation of high aspect ratio features is important to the success of sub-micron technology and to the continued effort to increase circuit density and quality of individual substrates and die.
High aspect ratio features are conventionally formed by patterning a surface of a substrate to define the dimensions of the features and then etching the substrate to remove material and define the features. To form high aspect ratio features with a desired ratio of height to width, the dimensions of the features are required to be formed with certain parameters, which is typically defined as the critical dimensions of the features. Reliable formation of high aspect ratio features with desired critical dimensions requires precise patterning and subsequent etching of the substrate.
Photolithography is a technique used to form precise patterns on substrates. In conventional photolithographic processes, a photoresist is applied on the layer or layers to be etched and the features to be etched in the layer, such as contacts, vias, or interconnects, are defined by exposing the photoresist to a pattern of light through a photolithographic substrate, or photomask, that defines the desired configuration of the features. A light source emitting ultraviolet (UV) light may be used to expose the photoresist to chemically alter the composition of the photoresist. The exposed, or alternatively, the unexposed photoresist material is then removed to expose the underlying material of the substrate and the retained photoresist material remains as an etch resistant pattern on the substrate. The exposed underlying material is then etched to form the desired features in the substrate.
Photolithographic photomasks, or reticles, typically comprise a substrate of an optically transparent silicon based material, such as quartz, having a light-shielding layer of metal, typically chromium, patterned on the surface of the substrate. The metal layer is patterned and etched to form features which define the pattern and correspond to the dimensions of the features to be transferred to the substrate patterned by the photolithographic process.
The deposition and etching of the photomask requires that the substrate be transferred and supported within a processing system. It has become desirable to utilize processing equipment and systems which are configured to process the substrates themselves to fabricate the photomasks. However, these systems are typically configured to process circular substrates and must be reconfigured to support and transfer rectangular photomasks. In addition, the systems used to support and transport the substrates used in photomask fabrication must carefully handle the substrates to prevent scratches and other defects from being formed on the substrates. These defects can alter the light transmission properties of the substrates and result in defective photomasks.
Therefore, there is a need for a method and apparatus for transferring and supporting substrates in processing systems which minimizes defect formation.
One aspect of the invention provides an apparatus for supporting a substrate on a pedestal or cathode in a processing chamber to minimize contact between the substrate and the chamber components during processing. In another aspect of the invention, a substrate handler blade is provided to support a substrate during transfer to minimize contact between the substrate handler and the substrate and to retain angular and linear alignment of the substrate on the blade.
The present invention generally provides a substrate support member design in a plasma etch chamber and a substrate handler blade design to minimize defect formation in a substrate during processing and handling of substrates. One aspect of the invention provides an apparatus for supporting a substrate comprising a support ring having one or more substrate support members mounted on the support ring, and one or more openings extending through the one or more substrate support members for accepting a substrate. Preferably, the one or more substrate support members include an upper portion, a lower portion, and a tapered portion disposed between the upper portion and the lower portion, where the lower portion has an inclined surface.
The apparatus for supporting a substrate may be used in a processing chamber comprising an enclosure defining a process region, a substrate support member having a support surface disposed in the enclosure, and a support ring coupled to the support surface and adapted to receive a substrate.
Another aspect of the invention provides a substrate handler blade comprising a base plate and one or more retaining wings extending from the base plate. The one or more retaining wings comprise a base portion, a vertical support position, and an end portion, preferably with the vertical support portion comprising an inward facing inclined surface.
The apparatus for supporting a substrate may also be used in a substrate processing system comprising a transfer chamber, at least one processing chamber having a substrate support member with a support surface and a support ring coupled to the support surface, the support ring adapted to receive a substrate, and a substrate handler disposed in the transfer chamber. Preferably, the substrate processing system further comprises a substrate handler blade including a base plate and one or more retaining wings extending from the base plate connected to the substrate handler.